Measurement and Interpretation of Fractional Exhaled Nitric Oxide

Abstract

Nitric oxide is produced by the human lungs and increases in response to type 2 inflammation. The level of fractional exhaled nitric oxide (FeNO) may reflect type 2 inflammation in the airways, which is related to eosinophilic inflammation and treatment responsiveness to corticosteroids. The FeNO test is a non-invasive, simple, and safe point-of-care test to evaluate airway inflammation. It has been standardized for clinical use and has been widely utilized in daily medical practice. However, various intrinsic and extrinsic factors can affect FeNO levels, and understanding and controlling such factors will improve the utility of this measure. The FeNO test can be used to confirm an asthma diagnosis, predict treatment responses to corticosteroids, and guide inhaled corticosteroid therapy for asthma treatment.